ontario



GQ BOWMAR.

PISTON,

APPLICATION FILED 050.24, 1920.

Patented Sept. 6, 1921.

FIG.

-I N VE NTO R GERSH'ON BOWMAR.

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GERSHON Bowman, or 'rono rro, oninnro, CANADA, Assisnon or ONE-HALF ToWILLIAM EDWARD HOLDER, or TORONTO, ONTARIO, CANADA.

ris'ron.

To all whom it may concern:

Be it known that I, WGERSHON BOWMAR, a subject of the King of GreatBritain, and a resident of the city of Toronto, in the county of York,in the Province of Ontario, Canada, have invented certain new and usefulImprovements in Pistons, of which the following is a specification.

My invention relates to improvements in pistons and the object of theinvention is to provide a piston characterized by a vacuum space formedin the head end of the piston which will be light, strong and durableand will retain its vacuum indefinitely.

To the attainment of the foregoing, the invention consists in theimprovement as hereinafter described and definitely claimed.

In the accompanying drawings, forming part of this specification:

Figure 1 is a sectional view through my piston and vacuum chamber.

Fig. 2 is a sectional view through a mold showing the vacuum chamber andthe metal forming the piston when poured into the mold.

Fig. 3 is a perspective detail of the vacuum chamber shown in Figs. 1and 2.

In the drawings like characters of reference indicate the correspondingparts in each figure, and for the sake of clearness the piston will bedescribed in connection with a method of making the same which will beclaimed in an application divisional of this.

1 indicates a piston. 2 is a vacuum chamber which is formed of sheetmetal which is non porous and which is cast within the piston 1 beingsecured to the core 3 of the mold as indicated in Fig. 2 by wires 4which are temporarily secured to the inner face of the vacuum chamber 2and extend into the body of the core. The wall 5 of the vacuum chamber 2is provided with a punched orifice 6.

It will be noted that the head of the core 3 is slightly smaller indiameter than the diameter of the vacuum chamber 2.

When the metal 7 forming the piston is poured into the mold it forms anannular shoulder 8 around the interior'of the piston serving to hold thevacuum chamber 2 in place. The inner wall 5 of the vacuum chamber isalso preferably provided with a series of annular corrugations 9 toallow for the expansion and contraction of the metal during heating andcooling. The vacuum cham-' Specification of Letters Patent.PatentedSept. 6, 1921. Application filed December 24, 1920. Serial No.4335007..- 1

her 2 is secured by the wires 4 tothe core 3 of the mold and is theninsertedin the mold and the metal 7 poured. When the metal is cooled andthe piston removed from the mold and the core removed the piston andvacuum chamber 2 are reheated to a temperature below the fusing point ofthe metal but sufiicient to form a vacuum within the chamber, theexpanding air passing out through the perforation 6. The perforation 6is then sealed as indicated at 10 (see Fig. 1) and the piston and vacuumchamber allowed to cool.

It has been found in practice that my construction of piston is the onlyone by which the vacuum can be retained in a piston with out undulyincreasing the weight of such piston as it is essential that such vacuumbe formed in a chamber of non-porous metal and not formed directly inthe piston which being formed of cast metal is porous and for thisreason the vacuum is soon destroyed unless the wall of the chamber bemade of such a thickness as to make the piston too heavy for practicaluse.

What I claim as my invention is:

1. In a piston, a piston body having a hollow interior, and a vacuumchamber formed of non-porous metal secured within the piston body so asto cover the interior face of the head thereof.

2. In a piston, a piston body having a hollow interior, a vacuum chamberformed of non-porous metal fitting within the piston so as to cover theinterior face of the head, the said piston body having a projectingportion formed in the interior thereof and bearing against the innerface of the chamber to retain it in place.

3. In a piston, a piston body formed with a hollow interior and havingan annular interior shoulder cast therearound, and a vacuum chamberfitting between the interior face of the head and the annular shoulderat its edge.

4. In a piston, the combination with a hollow piston body, of a vacuumchamber formed of non-porous material and located in the piston body;the said vacuum chamber being opposed to the inner side of the head ofthepiston body and being provided with the inner corrugated wall.

5. A piston having therein a chamber in which is avacuum or partialvacuum; the

said chamber being formed of non-porous material; the said chamber beinglocated adjacent to the head of the piston and having its wallremote'from the piston corrugated. V

6.. In a piston, apiston body having a hol- 10W interior and a vacuumchamber formed of non-porous metal secured Within the piston body.

7. In a piston, a piston body having a hollow interior and vacuumchamber formed of non-porous metal secured within the piston body andconstructed and arranged to expand and contract independently of thecontraction and expansion of the piston head.

8. In a piston, a piston havin a hollow interior and a vacuum chamberformed of non-porous metal secured to the inner side head. 7

GERSHON BOWMAR. V

